1. Field of the Invention
The present invention relates to polymer materials and more particularly to thermal responsive, water-soluble polymers.
2. Description of Related Art
Materials that adapt to environmental stimulations to change their own properties are called smart polymers. Smart polymers adapt to chemical or physical stimulations including temperature, pressure, pH value, and electric fields to initiate contracting or expanding and produce a change larger than 1,000 times their original size. Current development in smart watergel of smart polymers mainly seeks to (1) adapt to stimulations of different fields or different properties; (2) achieve a fast responsive property; and (3) respond within a small stimulation range. Due to the unique property of smart watergel, it is applied in various fields such as pharmaceuticals, chemistry, environmental engineering, and biological fields.
The solubility of most polymer materials increases as the temperature rises. Nevertheless, the solubility of smart watergel decreases as the temperature rises. This property is referred to as the lower critical solution temperature (LCST). This phenomenon is due to the hydrogen bonding between a hydrophilic portion of the polymer and the water molecule being stronger at low temperatures; thus it is dissoluble. When the temperature rises, the hydrophobic portions of the polymer have a stronger inter-reaction, causing a weakened reaction with hydrogen bonding of the water molecule, therefore the solubility is decreased.
Watergel is a three-dimensional polymer with a net structure that expands or contracts when adsorbing or abstracting the solvent. This characteristic makes the property of watergel fall between liquid and solid. Presently, the main limitations of the application of watergel in industry are the difficulties in shape, size, and phase variety. Researchers have been enthusiastically seeking how to apply smart watergel in biomedicines, drug release agents, and tissue engineering. Meanwhile, the temperature and pH value of watergel are the main factors to be controlled to adapt to human bodies. Consequently, to design a fast-response smart watergel having biological-compatibility (bio-degradable) is the current developmental goal.
A microfluidic chip is a chip full of capillary channels for small volume as microliter or even nanoliter fluid infused therewithin, to carry out manipulations in a laboratory such as mixing, isolating, culturing, heating, and the process of PCR (polymerase chain reaction) by means of mechanical or non-mechanical pumping. In the microfluidic chips for the isolating process, the biological materials to be isolated or cultured are contained in the isolating fluid. To achieve the best result, the isolating resolution and its fluidity of the isolating fluid in the capillary channels should be considered. Accordingly, applying smart watergel in microfluidic chips and controlling the temperature externally for viscosity variation in the capillary channel can improve the fluidity and resolution of the microfluid. When a utilizing polymer with a net structure to process high resolution isolating, the fluid with high molecule weight will not damage the structure or effect the fluidity due to the phase isolation created by temperature change.